1. Field of the Invention
The present invention relates to a sensor element manufactured by cutting out a laminated body formed by laminating ceramics green sheets, and a manufacturing method thereof.
2. Description of the Background Art
Conventionally, various measuring devices have been used for determining a concentration of a desired gas component in a measurement gas. A known device of measuring a NOx concentration in a measurement gas such as a combustion gas, for example, is a sensor having a Pt-containing electrode and a Rh-containing electrode formed on an oxygen ion conductive solid electrolyte, such as zirconia (ZrO2) (see Japanese Patent Application Laid-Open No. 8-271476, for example).
A sensor element of a gas sensor as recited in Japanese Patent Application Laid-Open No. 8-271476 is manufactured as follows: forming circuit patterns (hereinafter also referred to as merely a “pattern”) for a plurality of the sensor elements (e.g., several to several tens of the sensor elements) on each of a plurality of ceramics green sheets (hereinafter also referred to as merely a “green sheet”) including zirconia which is an oxygen ion conductive solid electrolyte as a ceramics component, laminating those green sheets and integrating them to obtain a laminated body, then cutting the laminated body to obtain a plurality of cutting elements (chips), and burning those cutting elements. The manufactured sensor element is stored in a ceramics housing and held by a plate spring which also functions as a contact point to an external connection electrode provided on a surface of the sensor element.
In the gas sensor manufactured by the above described method, breaks and cracks are often generated in a side end portion of a longitudinal direction of the sensor element by an end portion of the sensor element making a contact with a housing, causing yield deterioration of manufacturing the gas sensor. Specifically, it has been a problem that such breaks and cracks are notably generated in a side where a heater of the sensor element is provided. The inventors of the present invention has confirmed that this is because that the sensor element does not have outline dimension in accordance with a predetermined design.